Magnetic treatment of metals



F. L. BISHOP.

MAGNETIC TREAfMENT 0F METALS.

APPLICATION FILED IAN.2, Is14.

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F. L. BISHOP.`

MAGNETIC TREATMENT 0F METALS.

APPLICATTON FILED IAN.2, 1914.

Patented Aug. 15, 1916.

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azac@ FREDERIC L. BISHOP, OF PITTSBURGH, PENNSYLVANIA.

MAGNETIC TREATMENT OFMETALS.

Speoication of Letters Patent.

Patented Aug. 15, 1916.

Application led January 2, 1914. Serial No. 809,831.

To all lwhom t may concern.' y

Be it known that I, FREDERIC L. .B Isnor, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and' on the line II-II, of Fig. 1; Fig. 3 isa p wiring diagram showing coils, circuits, and one form of current regulator; Fig. 41s a detail View showing a part of the current regulator; and Fig. 5 is a vertical section illustrating a quenching tank which may be employed. c 1 In my pending application, Serial No. 750,844, filed February 26, 1913, I have de- `scribed and claimed the treatment of solid metal, particularly iron and steel, for the purpose of altering its molecular structure, which consists in subjecting the metal to the action of the magnetic field of an alternating electric current, the indirect current in the `'metal being utilized to heat the metal while being so treated. As set forth in .my said application, I find that this treatment changes the molecular structure of the metal in a highly benecial manner. I haveI now discovered that the best results are obtained when the metal being treated is heated to or slightly above its recalescence point depending upon the use to which the metal is to be put, the action of the magnetic field upon the metal being continued during the entire process. I have also discovered that the changes in magnetic properties ofthe metal when heated through its recalescence point may be utilized to automatically indicate when the treatment of the metal is completed, and also to automatically regulate the magnetic and heating action. y

Other improvements in the method of treatment will hereinafter appear. I

My invention also consists in the provision of simple kapparatus forcarrying out my improved method.

Referring to the accompanying drawings, the numeral 2 designates a suitable caseor lclosure, preferably constructed of heat insulating material, .and Within Which the 'to the novel treatment.

metal objects indicated at A and Bare designed to be placed while being subjected The apparatus shown 1n F1 s. 1 and 2 is designed for the treatment o two pieces of metal simultaneously. For this purpose I provide wlthin thecasing or closure 2, two hollow co1ls 3, placed side by side. These coils have within them a lining 4 of` non-conducting materlal such as clay, terra cotta or mica. I also 4preferably vplace within the linings 4 a metalining 5 which serves to protect the linings 4 from direct contact with the metal. This inner shell 5 may be in the form of a closed cylinder, in which induced eddy currents will circulate, as shown at the left hand side of Fig. 2; or it maybe divided lntol segments, as shown at the right hand side of Fig. 2, to prevent the circulation of induced electric currents therein. vThe magnetic circuits of the coils or windings 3 are The lower ends of the hollow coils are arranged to be closed by means of doors 8 havmg removablepivots 9 and arranged to be held closed by means ofv suitable latch decompleted through the metallic head blockw vices 10. Each of thecoils or windings 3 is preferably composed of a number of separate coils 3, as shown in Fig. 3. These coils are arranged 'to receive current from an alternating generator 11l through a current regulating switch 12 by means of which the coils may be connected in various ways. The terminals of the several coils 3 are vconnected to the series of relatively fixed contact fingers 13 which are arranged to be engaged by a series of movable contacts 14.' This movable contact member is shown as having five positions with respect to the contacts 13, namely, the open circuit position in which the parts are shown in Fig. 3, and the positions indicated by the several dotted lines a, a, b, 6,0, c., d, d; the position d, d being an open circuit position. Without tracing out the circuits of the coils in detail in the several positions ofthe current regulating switch, it will be readily seen that in the position a, 'a all the coils will be connected in parallel; that in the position b, b the two upper coils will be connected in series with each other and in parallel with the two lower coils; Vand that l in the position c, c all four coils will be connected in series.

As before indicated, I have discovered that I can make usc of thev changes in the magnetic properties of the metal being treated to automatically control the treating circuit for the coils.

operation'and to cut off the current when the desired "treatment is complete. For this purpose it is necessary to provide the member of the current regulating switch whlch carries the movable contacts 14 with an actuating device capable of eHecting a step by step movement of said member as the current in the circuit of the coils 3 changes. This may be accomplished in various ways. In, the current regulator shown in Figs. 8 and 4, the member carrying the contacts 14 is arranged to be moved laterally with respect to the contacts 18 and is connected .to a movable plunger 15. This plunger at its vopposite end extends within thev closed receptacle V16 designed to be partially filledwith oil or other suitable liquid, and carries therein a piston composed of a plurality of separated plates 17. These plates are provided with perforations 18 adapted to per mit of a relatively slow circulation of the oil therethrough. The piston is provided with-a series of teeth or notches 19 for engagement with a pivoted dog 20 which forms the armature of an electro-magnet 21 which is connected in series in the supply The armature dog 20 has a lever arm 22 connected thereto and carries an adjustable counterweight 23. The armature dog 20 is arranged to hold the rod or plunger 15 against the 'action of a counterweight 24 connected thereto.

The operation is as follows: The metal objects A and B to be treated are first set upon the doors 8, which have been detached from the apparatus by the removal of the pivots 9. The casing or closure 2 is (by a craneor any other suitable means) brought over the said metal objects and dropped over them so that they are inclosed within the coils or windings in the manner shown in Figs. l and 2. The pins 9 are then inserted and the doors are secured by the latches 10. The entire apparatus is then moved overpthe pit or other support shown in Fig. 1 and placed in such position thereon that the base block 7 of magnetic material is directly below the pieces A and B. The necessary circuit connections for the coils are then established and the current regulating switch is manually moved to the position indicated by the dotted line a, a. The several coils 3a of each winding remain connected in parallel until the metal is preferably heated to a temperature near the recalescence point of the metal. At this time the changes in the magnetic properties of the metal tend to allow a material increase in thevflow of current thrOugh the coils. This increased. flowv of current energizes the magnet 21 to an extent where it will overcome the action of the counterweight 23 and will attractl the armature dog 20, thus releasing said dog from its engagement with the rod or plunger 15. The counterweight '24: now acts to remove said rod or plunger against the action of the oil in the receptacle 16 and at a total distance substantially equal to the distance between adjacent notches or teeth of said plunger where it is stopped by the resistance of the oil. This connects the coils 3 in series-parallel, thus increasing their resistance and cutting down the How of current proportionately to such increase. This weakens the magnet 21, and the armature dog now drops into engagement vwith the next tooth or notch. As the temperature of the pieces A and B continues to increase, a further increase in current takes place in the circuit of the said coils, resulting in another step movement of the regulator and so onuntil the proper treatment has been given to the metal when the circuit is opened by the regulator. In this manner the proper limit of temperature is not only automatically indicated, but'the current is automatically shut ofl" and heating beyond such temperature is prevented. It will be understood, however, that for certain purposes the predetermined temperature may be other than that above described. That is to say, the device may be so adjusted that Vit will shut off the current before the recalescence point is reached, if this should be desirablev in any particular case. In some cases also it may be desirable to carry the heating beyond the recalescence point and beyond the temperature at which the metal loses its magnetic properties. In such case the coils 3 may be used as resistance units and the material heated directly from said coils, instead of by the action of the currents induced in the metal. After the treatment is completed, the apparatus may be removed from the pit or other support and carried over a quenching tank containing the quenchingr liquid. The bottom doors 8 can then be rcleased and the pieces A and B dropped, while still in the vertical position, directly into the tank. This is a feature of importance since by dropping the pieces into the tank in vertical position a uniform cooling is obtained. In this connection I may employ a tank having means by which the rate of cooling of the piece being treated can be accurately controlled. One forni of such tank is shown in Fig. 5. In this figure, 25 designates the tank proper, and 26 an inner compartment thereof having perforated lateral walls. This inner compartment may be made of any desired area in cross section relative to the cross-sectional area of the piece being treated, and thereby (in the manner of a dash-pot) regulating the time required for the piece to become immersed therein. The cooling can be furthe-r regulated by the size of the perforations in the wall of the compartment.

rl`l1e tank 25 should be provided with a heavy bottom 27 sufficiently strong-to stand the shocks when the pieces are dropped suddenly thereon. The heating above described being also of a uniform character, very exact results in annealing and tempering of the metal can be obtained and these results can be accurately reproduced in successive pieces. In some cases, however, it may be desired to slowly cool the treated metal While still under the action of the magnetic field. This can be readily effected by properly controlling the current in the heating coils. By employing an inner shell or lining 5 of a character to permit the circulation of induced currents therein, such shell or lining ma be very quickly heated and may bemade to impart heat directly to the metal objects.

I preferably employ an alternating currentvention is susceptible of many modifications,

within the spirit and scope of the appended claims. Thus, instead of being arranged to treat two ypieces at once, it may be arranged to treat one piece, or more than two pieces. The general construction and arrangement of the apparatus may be'widely`yaried; the number of sections or units of the coils may be varied; any suitable form of current regulating switch may be employed, and other changes may be made.

lVhat I claim is:

1. The herein described method of treating metal to alter its molecular structure, which consists in heating the metal above its recalescence point and subjecting it to the action of the magnetic field produced by an alternating current While being heated; substantially as described.

2. The method of treating metal to alter its molecular structure, which comprises ,cooling the metal from a point above its recalescence point and subjecting it to the action-of a magnetic field of an alternating current While cooling; substantially as de-' scribed.

3. The method of treating metal to alter its molecular structure, which consists in heating the metal and at the same time subjecting it to the action of a varying magnetic field, and utilizing the changes in the magnetic properties of the metal during the treatment to automatically control the current producing such field; substantially as described.

4. The method of treating metal to alter its molecular structure, which comprises subjecting the metal to the action of the .and While the metal is subject thereto; substantially as described.

`5. The method of treating metal to alter its molecular structure, which comprises subjecting the metal to the action of' the magnetic field produced by an alternating current, heating the metal through its recalescence point by the action of such field on the metal and While the metal is subject thereto, and causin thechanges in the magnetic properties ofthe metal under treatment to automatically control thecurrent producing saidfield; substantially as described. v

6. The method of treating metal to alter its molecular structure, which comprises subjecting the metal to the action of the magnetic field produced by an alternating current, heating the metal through its recalescence point by the action of such field and While the metal is subject thereto, and causing the changes in the magnetic properties of the metal being treated to automatically indicate When the predetermined heating tem erature has been reached escribed. 7. The method of treating metal to alter its molecular structure which comprises subjecting the metal to the action of the magnetic field produced by an alternating current, heating the metal through its lrecalescence point by the action of such field and While the metal is subject thereto, and causing the changes in the magnetic properties of the metal being treated to automatically indicate when the predetermined heating temperature has been reached and to cut ofi the current producing such field when the predetermined temperature is reached; substantially as described.

8. The method of treating metal to alter its molecular structure,.which consists in subjecting the metalto the action of the magnetic field produced by an alternating current, causing such magnetic field to heat the metal during such treatment to a predetermined temperature, and utilizing the .changes in the y: magnetic properties of the metal to automatically indicatev When the predetermined temperature has been reached substantially las described.

9. The herein described method of treating metal to alter its molecular structure, which comprises placing the metal within the magnetic field of a coil or Winding carrying an alternating current, and Varying` the resistance: of such Winding during the treatment; substantially 'as described.

10. The herein described method of treat'- ing metal to alter its molecular structure,

' which comprises placing the metal within the magnetic eld of a coil or winding carsubstantially rying an alternating current, and automatically varying the resistance of such Winding during the treatment; substantially as described.

11. The herein described method of treating metal to alter its molecular structure, which comprises placing the metal Within the magnetic field of a coil or Winding carrying an alternating current, and causing the changes in magnetic properties of the metal being treated during such treatment to automatically vary the resistance of the winding; substantially as described.

l2. 'lhe method of treating metal to alter its molecular structure, Which comprises subjecting the metal to the magnetic field produced by a coil or Winding carrying an alternating current, and 'causing the changes produced in the magnetic properties of the metal, during the treatment to control the supply of current to said winding; substantially as described.

13. The method of treating metal to alter its molecular structure, which comprises the subjecting of the metal to theaction of the magnetic field of a coil or Winding carrying an alternating current, causing such field to heat the metal to a point at which yits permeability becomes small, and then tric current, and causing said current tQ produce eddy currents in a heating member adjacent to the member; substantially as described.

In testimony whereof, I have hereunto set my hand.

FREDERIC L. BISHOP. Witnesses:

W. C. LYON, H. M. CoRwIN. 

